Journey To The Desert's Edge, Part 11

Note: this is the eleventh in a series of occasionally appearing entries focusing on deserts in general and the drylands of West Texas in particular

“One reason that Texas is so drought prone is its latitude, the same latitude as the Sahara Desert.  As in the Sahara, large high-pressure cells can sit over the state for weeks or months at a time and block storms and incoming moisture.  The cause of these cells is not well understood but possible influences are solar storm cycles, ocean temperature cycles (El Nino and La Nina), and global warming.”-- Andrew Sansom, Water In Texas: An Introduction, 2008

Men’s lives in a place have always been influenced by climate: a truth...

For centuries, the western Concho Valley of Texas has been a sparsely land due to its harsh and demanding climate.  When the Spanish explored the area in the 1600s, they found people we know today as the Jumanos, some of whom lived in small rancherias along the river and some of whom practiced a more nomadic lifestyle.  By the latter half of the Seventeenth Century, the Jumanos found themselves displaced by the Lipan Apache who for a time, controlled barren lands between the Colorado River of Texas and the Rio Grande.  Next came the Comanche...

The concept of large permanent settlements came fairly late to this land of short grass and cactus.  It wasn’t until 1870 that a thousand people lived in what is now present day Tom Green County and most of those made their homes near Fort Concho, one of several remote military outposts established after the Civil War to bring law and order to western Texas...

The Lipan Apache, seen here in a painting by George Nelson, changed their lifestyle after the introduction of the horse and abandoned the traditional wikiup dwelling in favor of the tipis favored by Plains tribes

In the dry country surrounding the Fort, ranching became a way of life.  Later settlers tried their hand at farming.  Both activities were heavily dependent on the sporadic rains occasionally falling on sun-baked land.  Both activities would ultimately disrupt the fragile ecology of a semi-arid desert.  But these are stories for another day...

Uncertainty is the name of the game when it comes to knowing what happens tomorrow (or even later today): a second truth...

As a consequence, astrologers and other folks with prognostication skills in fields like tea-leaf analysis and sheep entrail reading have enjoyed steady employment for millenia.  The problem is that accurate predictions based on planetary locations one day are usually followed by multiple weeks of being wrong.  It’s a flaw that encourages skepticism among scientists who tend to believe theories should be considered faulty if reality disproves predictions based upon those theories...

Man's attempt to foresee changes in

weather dates at least to the days

of the ancient Babylonians

Science really doesn’t like uncertainty but efforts by scientists to provide us with a clear picture of Earth’s future climate is no easy task.  This difficulty may offer some comfort to those who prefer to ignore the overwhelming evidence of global warming.  But the facts do not take the side of climate ostriches who believe that we’re merely having a couple warm years before things go back to normal.  Sea levels are rising, Arctic ice levels are decreasing, lower troposphere temperatures are increasing...

Where global warming leads the United States in terms of long term effects is a mixed bag.  Models show average daily temperatures will continue to rise but will do so unevenly both in terms of time and location.  Frost free times of the year and growing seasons will lengthen, especially in the western half of the United States.  Projections for precipitation are that it can be expected to increase in the winter and spring in the north.  But the rains and snow are likely to decrease in the Southwest during those seasons as well.  Heat waves will be more common everywhere with periods of drought lasting longer in the already arid Southwest.  For those who dislike frozen winter days, there is the promise that cold waves are likely to become less intense over time.  Those who live along the coasts can expect sea levels to rise and for hurricanes to become stronger and more dangerous...

A good deal of global warming can be tied to an increase in greenhouse gases (which include water vapor, carbon dioxide, methane, nitrous oxide, and ozone) in the atmosphere.  Greenhouse gases absorb and emit radiation in the thermal infrared range.  This is not necessarily bad-- the radiation from greenhouse gases in the atmosphere raise a planet’s surface temperature to a level above what it would be if the planet had no atmosphere.  Without an atmosphere, Earth’s surface temperature would likely be about 0 degrees Fahrenheit...

West Texas sheep rancher as depicted in a mural

by Stylle Read

But too much atmospheric warming is not a good thing.  Our planetary neighbor Venus enjoys mean surface temperatures of about 863 degrees Fahrenheit thanks to the greenhouse effect and an atmosphere which is roughly 96% carbon dioxide...

Overwhelming numbers of scientists believe human activity, particularly human activity increasing the amount of greenhouse gases in the atmosphere, is a major factor in the global warming now taking place.  Lest the reader be tempted to believe this assertion is a new-fangled notion fostered by enemies of the energy companies, we note Alexander Graham Bell expressed concern in 1917 with our continued fossil-fuel use as ultimately causing a terrestrial “hot house effect” versus a “greenhouse effect”... 

The level of carbon dioxide emissions generated by human activity is particularly critical in understanding future climate on earth.  Studies of ice core samples reveal a carbon dioxide concentration of about 270 parts per million (ppm) in the years immediately before the Industrial Revolution.  By 1960, the level had increased to 313 ppm.  By 2013, carbon dioxide concentrations were at 400 ppm.  This rapidly rising number (and attendant global warming) can be traced primarily to human activities such as burning fossil fuels and tropical deforestation...

Global warming travels with problems for humans, the species largely responsible, for it and the severity of future climate changes it brings may be in the hands of those same humans.  In terms of the effects we noted earlier, we might point out rising sea levels impact the habitability of coastlines.  Likewise, higher temperatures and the likelihood of increased precipitation in some areas and prolonged drought in others affect agricultural production...

Dire predictions for the future of the planet as a whole set aside, we all have a localized interest in what changing weather brings.  What does global warming mean for me, I ask... 

My home is a semi-arid area at the edge of the Chihuahuan Desert with an average annual rainfall of about 20 inches.  This average, however, may not entirely what it would be if man let Mother Nature take her own course.  For roughly two decades, cloud seeding operations have been used to enhance area rainfall.  A study conducted for the city of San Angelo suggests rainfall during the 1985-1989 period increased at least 25% in seeded areas during the months seeding operations took place...

Ranchland in the western Concho Valley

What effect cloud seeding ultimately will have on area rainfall averages remains to be seen.  In the fifty years prior to consistent cloud seeding, San Angelo averaged 19.08 inches of precipitation per year with individual years totaling as low as 7.41 inches and as high as 40.40 inches.  Since folks began injecting cumulus clouds with silver iodide, annual average rainfall has increased to 21.58 inches with individual year extremes ranging from 9.21 to 32.93 inches...

(Compounding the difficulty of short-term assessments of long-term climate change as it occurs in the Concho Valley is the fact precipitation in the dry country is erratic.  While a given year’s rain in semi-arid regions is usually within ± 50% of the statistical average, there is no guarantee amounts that actually fall will be in that range.  Additionally, the monthly deviation from statistical norms can be (and usually are) significant.  The month of May offers a good example.  With an annual average rainfall of 02.82 inches, May sits statistically as the “wettest month of the year” for San Angelo.  But actual monthly totals from 2005 to 2016 range from 0.12 inches to 9.12 inches.)

Alexander Graham Bell, father of the

telephone and prophet of global warming

Although cloud seeding likely helps raise reservoir levels, it makes analyzing effects of global warming on natural precipitation patterns and evaporation rates in this sector of Texas more difficult.  This is dry country by nature--  we can look at data collected by the Texas A&M agricultural research station near San Angelo over a 54 year period and see the site’s 19.20 inches of precipitation was offset by a potential evapotranspiration rate of 71.34 inches.  Any increase in average annual rainfall derived from either cloud seeding or precipitation pattern changes induced by global warming may not prove to be as useful as hoped if rising temperatures lead to higher evaporation rates...

Scientists suspect rainfall may gradually lessen in already arid South and West Texas.  As temperatures continue to rise and warm air blankets the state for longer periods of time, meeting points between cold and warm air masses will shift and push seasonal rains more to the north and east...

Probably a lot of long hot summer days for my part of the world down the road...

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CREDITS

Note: All photographs and information for this essay were located through Google Images, Wikipedia and readily available general information sources such as Enclcopedia Brittanica, without authoritative source or ownership information except as noted: photographs of Stylle Read mural and Concho Valley ranchland by Louis R Nugent; George Nelson Lipan Apache painting from http://www.forttumbleweed.net/apachepass.html ; water supply sustainability from https://data.globalchange.gov/assets/36/96/d21cee93238d81f9ea1404f06c5d/ECO_water_risk_index_V2.png; average Texas summer temperature increase from http://images1.dallasobserver.com/imager/u/745xauto/7439644/climatemaps.jpg ; Alexander Graham Bell photograph from  http://www.telcomhistory.org/vm/Images/AGB1867.jpg ; Information on general effects of climate change from  http://climate.nasa.gov/effects/; the Future of Climate Change from https://www.epa.gov/climate-change-science/future-climate-change; evidence for global warming from https://www.skepticalscience.com/evidence-for-global-warming.htm; rainfall increase from cloud seeding from https://www.tdlr.texas.gov/weather/weatherfaq.htm; nature of semi-arid precipitation patterns from http://www.fao.org/docrep/t0122e/t0122e03.htm; future rainfalls likely more to north and east from https://www.texastribune.org/2014/07/14/state-only-planning-bigger-texas-not-hotter-one/